Cu–ZSM-5, Cu–ZSM-11, and Cu–ZSM-12 catalysts for direct NO decomposition

Cu–ZSM-5 has for many years been recognized as a unique catalyst for direct NO decomposition. Here, it is discovered that both Cu–ZSM-11 and Cu–ZSM-12 are about twice as active as Cu–ZSM-5. This difference is attributed to the active sites located almost exclusively in the straight zeolite pores. In situ EPR results suggest that higher activity is related with improved accessibility of these sites. Thus, it is clear that contrary to previous observations, the special pore structure of Cu–ZSM-5 is not a decisive factor for catalytic activity in NO decomposition.